Rename "FB CMA" helpers to "FB DMA" helpers - considering the hierarchy
of APIs (mm/cma -> dma -> fb dma) calling them "FB DMA" seems to be
more applicable.

Besides that, commit e57924d4 ("drm/doc: Task to rename CMA helpers")
requests to rename the CMA helpers and implies that people seem to be
confused about the naming.

In order to do this renaming the following script was used:

```
	#!/bin/bash

	DIRS="drivers/gpu include/drm Documentation/gpu"

	REGEX_SYM_UPPER="[0-9A-Z_\-]"
	REGEX_SYM_LOWER="[0-9a-z_\-]"

	REGEX_GREP_UPPER="(${REGEX_SYM_UPPER}*)(FB)_CMA_(${REGEX_SYM_UPPER}*)"
	REGEX_GREP_LOWER="(${REGEX_SYM_LOWER}*)(fb)_cma_(${REGEX_SYM_LOWER}*)"

	REGEX_SED_UPPER="s/${REGEX_GREP_UPPER}/\1\2_DMA_\3/g"
	REGEX_SED_LOWER="s/${REGEX_GREP_LOWER}/\1\2_dma_\3/g"

	# Find all upper case 'CMA' symbols and replace them with 'DMA'.
	for ff in $(grep -REHl "${REGEX_GREP_UPPER}" $DIRS)
	do
	       sed -i -E "$REGEX_SED_UPPER" $ff
	done

	# Find all lower case 'cma' symbols and replace them with 'dma'.
	for ff in $(grep -REHl "${REGEX_GREP_LOWER}" $DIRS)
	do
	       sed -i -E "$REGEX_SED_LOWER" $ff
	done

	# Replace all occurrences of 'CMA' / 'cma' in comments and
	# documentation files with 'DMA' / 'dma'.
	for ff in $(grep -RiHl " cma " $DIRS)
	do
		sed -i -E "s/ cma / dma /g" $ff
		sed -i -E "s/ CMA / DMA /g" $ff
	done
```

Only a few more manual modifications were needed, e.g. reverting the
following modifications in some DRM Kconfig files

    -       select CMA if HAVE_DMA_CONTIGUOUS
    +       select DMA if HAVE_DMA_CONTIGUOUS

as well as manually picking the occurrences of 'CMA'/'cma' in comments and
documentation which relate to "FB CMA", but not "GEM CMA".

This patch is compile-time tested building a x86_64 kernel with
`make allyesconfig && make drivers/gpu/drm`.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com> #drivers/gpu/drm/arm
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220802000405.949236-3-dakr@redhat.com